Proper handling of failing to bind server socket

src/connection.cpp

@@ -986,8 +986,16 @@ nextpeer:
 void Connection::serve(u16 port)
 {
 	dout_con<<getDesc()<<" serving at port "<<port<<std::endl;
+	try{
 		m_socket.Bind(port);
 		m_peer_id = PEER_ID_SERVER;
+	}
+	catch(SocketException &e){
+		// Create event
+		ConnectionEvent e;
+		e.bindFailed();
+		putEvent(e);
+	}
 }
 
 void Connection::connect(Address address)
@@ -1597,6 +1605,9 @@ u32 Connection::Receive(u16 &peer_id, SharedBuffer<u8> &data)
 			if(m_bc_peerhandler)
 				m_bc_peerhandler->deletingPeer(&tmp, e.timeout);
 			continue; }
+		case CONNEVENT_BIND_FAILED:
+			throw ConnectionBindFailed("Failed to bind socket "
+					"(port already in use?)");
 		}
 	}
 	throw NoIncomingDataException("No incoming data");

src/connection.h

@@ -59,6 +59,14 @@ public:
 	{}
 };
 
+class ConnectionBindFailed : public BaseException
+{
+public:
+	ConnectionBindFailed(const char *s):
+		BaseException(s)
+	{}
+};
+
 /*class ThrottlingException : public BaseException
 {
 public:
@@ -424,6 +432,7 @@ enum ConnectionEventType{
 	CONNEVENT_DATA_RECEIVED,
 	CONNEVENT_PEER_ADDED,
 	CONNEVENT_PEER_REMOVED,
+	CONNEVENT_BIND_FAILED,
 };
 
 struct ConnectionEvent
@@ -447,6 +456,8 @@ struct ConnectionEvent
 			return "CONNEVENT_PEER_ADDED";
 		case CONNEVENT_PEER_REMOVED: 
 			return "CONNEVENT_PEER_REMOVED";
+		case CONNEVENT_BIND_FAILED: 
+			return "CONNEVENT_BIND_FAILED";
 		}
 		return "Invalid ConnectionEvent";
 	}
@@ -470,6 +481,10 @@ struct ConnectionEvent
 		timeout = timeout_;
 		address = address_;
 	}
+	void bindFailed()
+	{
+		type = CONNEVENT_BIND_FAILED;
+	}
 };
 
 enum ConnectionCommandType{

src/server.cpp

@@ -109,6 +109,10 @@ void * ServerThread::Thread()
 		{
 			infostream<<"Server: PeerNotFoundException"<<std::endl;
 		}
+		catch(con::ConnectionBindFailed &e)
+		{
+			m_server->setAsyncFatalError(e.what());
+		}
 	}
 	
 	END_DEBUG_EXCEPTION_HANDLER(errorstream)
@@ -837,6 +841,7 @@ Server::Server(
 	m_path_world(path_world),
 	m_path_config(path_config),
 	m_gamespec(gamespec),
+	m_async_fatal_error(""),
 	m_env(NULL),
 	m_con(PROTOCOL_ID, 512, CONNECTION_TIMEOUT, this),
 	m_authmanager(path_world+DIR_DELIM+"auth.txt"),
@@ -865,6 +870,9 @@ Server::Server(
 	m_step_dtime_mutex.Init();
 	m_step_dtime = 0.0;
 
+	if(path_world == "")
+		throw ServerError("Supplied empty world path");
+	
 	if(!gamespec.isValid())
 		throw ServerError("Supplied invalid gamespec");
 	
@@ -1079,6 +1087,8 @@ Server::~Server()
 void Server::start(unsigned short port)
 {
 	DSTACK(__FUNCTION_NAME);
+	infostream<<"Starting server on port "<<port<<"..."<<std::endl;
+
 	// Stop thread if already running
 	m_thread.stop();
 	
@@ -1128,6 +1138,11 @@ void Server::step(float dtime)
 		JMutexAutoLock lock(m_step_dtime_mutex);
 		m_step_dtime += dtime;
 	}
+	// Throw if fatal error occurred in thread
+	std::string async_err = m_async_fatal_error.get();
+	if(async_err != ""){
+		throw ServerError(async_err);
+	}
 }
 
 void Server::AsyncRunStep()

src/server.h

@@ -545,6 +545,11 @@ public:
 	
 	std::string getWorldPath(){ return m_path_world; }
 
+	void setAsyncFatalError(const std::string &error)
+	{
+		m_async_fatal_error.set(error);
+	}
+
 private:
 
 	// con::PeerHandler implementation.
@@ -658,6 +663,9 @@ private:
 	// Equivalent of /usr/share/minetest/server
 	std::string m_path_share;
 	
+	// Thread can set; step() will throw as ServerError
+	MutexedVariable<std::string> m_async_fatal_error;
+	
 	// Some timers
 	float m_liquid_transform_timer;
 	float m_print_info_timer;